1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::sugg::Sugg;
3 use clippy_utils::ty::is_type_diagnostic_item;
5 can_move_expr_to_closure, eager_or_lazy, higher, in_constant, is_else_clause, is_lang_ctor, peel_blocks,
6 peel_hir_expr_while, CaptureKind,
8 use if_chain::if_chain;
9 use rustc_errors::Applicability;
10 use rustc_hir::LangItem::OptionSome;
11 use rustc_hir::{def::Res, BindingAnnotation, Expr, ExprKind, Mutability, PatKind, Path, QPath, UnOp};
12 use rustc_lint::{LateContext, LateLintPass};
13 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 declare_clippy_lint! {
18 /// Lints usage of `if let Some(v) = ... { y } else { x }` which is more
19 /// idiomatically done with `Option::map_or` (if the else bit is a pure
20 /// expression) or `Option::map_or_else` (if the else bit is an impure
23 /// ### Why is this bad?
24 /// Using the dedicated functions of the `Option` type is clearer and
25 /// more concise than an `if let` expression.
27 /// ### Known problems
28 /// This lint uses a deliberately conservative metric for checking
29 /// if the inside of either body contains breaks or continues which will
30 /// cause it to not suggest a fix if either block contains a loop with
31 /// continues or breaks contained within the loop.
35 /// # let optional: Option<u32> = Some(0);
36 /// # fn do_complicated_function() -> u32 { 5 };
37 /// let _ = if let Some(foo) = optional {
42 /// let _ = if let Some(foo) = optional {
45 /// let y = do_complicated_function();
53 /// # let optional: Option<u32> = Some(0);
54 /// # fn do_complicated_function() -> u32 { 5 };
55 /// let _ = optional.map_or(5, |foo| foo);
56 /// let _ = optional.map_or_else(||{
57 /// let y = do_complicated_function();
61 #[clippy::version = "1.47.0"]
62 pub OPTION_IF_LET_ELSE,
64 "reimplementation of Option::map_or"
67 declare_lint_pass!(OptionIfLetElse => [OPTION_IF_LET_ELSE]);
69 /// Returns true iff the given expression is the result of calling `Result::ok`
70 fn is_result_ok(cx: &LateContext<'_>, expr: &'_ Expr<'_>) -> bool {
71 if let ExprKind::MethodCall(path, &[ref receiver], _) = &expr.kind {
72 path.ident.name.as_str() == "ok"
73 && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(receiver), sym::Result)
79 /// A struct containing information about occurrences of the
80 /// `if let Some(..) = .. else` construct that this lint detects.
81 struct OptionIfLetElseOccurence {
88 fn format_option_in_sugg(cx: &LateContext<'_>, cond_expr: &Expr<'_>, as_ref: bool, as_mut: bool) -> String {
91 Sugg::hir_with_macro_callsite(cx, cond_expr, "..").maybe_par(),
102 /// If this expression is the option if let/else construct we're detecting, then
103 /// this function returns an `OptionIfLetElseOccurence` struct with details if
104 /// this construct is found, or None if this construct is not found.
105 fn detect_option_if_let_else<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<OptionIfLetElseOccurence> {
107 if !expr.span.from_expansion(); // Don't lint macros, because it behaves weirdly
108 if !in_constant(cx, expr.hir_id);
109 if let Some(higher::IfLet { let_pat, let_expr, if_then, if_else: Some(if_else) })
110 = higher::IfLet::hir(cx, expr);
111 if !is_else_clause(cx.tcx, expr);
112 if !is_result_ok(cx, let_expr); // Don't lint on Result::ok because a different lint does it already
113 if let PatKind::TupleStruct(struct_qpath, [inner_pat], _) = &let_pat.kind;
114 if is_lang_ctor(cx, struct_qpath, OptionSome);
115 if let PatKind::Binding(bind_annotation, _, id, None) = &inner_pat.kind;
116 if let Some(some_captures) = can_move_expr_to_closure(cx, if_then);
117 if let Some(none_captures) = can_move_expr_to_closure(cx, if_else);
120 .filter_map(|(id, &c)| none_captures.get(id).map(|&c2| (c, c2)))
121 .all(|(x, y)| x.is_imm_ref() && y.is_imm_ref());
124 let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
125 let some_body = peel_blocks(if_then);
126 let none_body = peel_blocks(if_else);
127 let method_sugg = if eager_or_lazy::switch_to_eager_eval(cx, none_body) { "map_or" } else { "map_or_else" };
128 let capture_name = id.name.to_ident_string();
129 let (as_ref, as_mut) = match &let_expr.kind {
130 ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
131 ExprKind::AddrOf(_, Mutability::Mut, _) => (false, true),
132 _ => (bind_annotation == &BindingAnnotation::Ref, bind_annotation == &BindingAnnotation::RefMut),
134 let cond_expr = match let_expr.kind {
135 // Pointer dereferencing happens automatically, so we can omit it in the suggestion
136 ExprKind::Unary(UnOp::Deref, expr) | ExprKind::AddrOf(_, _, expr) => expr,
139 // Check if captures the closure will need conflict with borrows made in the scrutinee.
140 // TODO: check all the references made in the scrutinee expression. This will require interacting
141 // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
142 if as_ref || as_mut {
143 let e = peel_hir_expr_while(cond_expr, |e| match e.kind {
144 ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
147 if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(local_id), .. })) = e.kind {
148 match some_captures.get(local_id)
149 .or_else(|| (method_sugg == "map_or_else").then(|| ()).and_then(|_| none_captures.get(local_id)))
151 Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
152 Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
153 Some(CaptureKind::Ref(Mutability::Not)) | None => (),
157 Some(OptionIfLetElseOccurence {
158 option: format_option_in_sugg(cx, cond_expr, as_ref, as_mut),
159 method_sugg: method_sugg.to_string(),
160 some_expr: format!("|{}{}| {}", capture_mut, capture_name, Sugg::hir_with_macro_callsite(cx, some_body, "..")),
161 none_expr: format!("{}{}", if method_sugg == "map_or" { "" } else { "|| " }, Sugg::hir_with_macro_callsite(cx, none_body, "..")),
169 impl<'tcx> LateLintPass<'tcx> for OptionIfLetElse {
170 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
171 if let Some(detection) = detect_option_if_let_else(cx, expr) {
176 format!("use Option::{} instead of an if let/else", detection.method_sugg).as_str(),
180 detection.option, detection.method_sugg, detection.none_expr, detection.some_expr,
182 Applicability::MaybeIncorrect,